Tissue ablation is used in numerous medical procedures to treat a patient. Ablation can be performed to remove undesired tissue such as cancer cells. Ablation procedures may also involve the modification of the tissue without removal, such as to stop electrical propagation through the tissue in patients with an arrhythmia. The ablation is often performed by passing energy, such as electrical energy, through one or more electrodes causing the tissue in contact with the electrodes to heats up to an ablative temperature, but may also be performed by freezing the tissue with the use of a cryoablation catheter.
Cryoablation catheters typically include an expandable element, such as a balloon, at the distal end. Although there are significant advantages of using balloons for cryoablation techniques, there are often associated disadvantages. First, to provide adequate attachment strength between a balloon and the catheter, the distal end of the balloon is often attached to a device distal tip, which may extend distally beyond the balloon. A balloon catheter with a distal tip can be difficult to position within the body, for example the right or left atrium of the heart. For a cryoablation technique to be effective, the distal end must be articulated with great accuracy to contact the balloon with the target tissue. Additionally, this technique is often performed in a very small space. A catheter with a long distal tip (one that extends past the distal neck of the balloon) or a balloon with extended distal and/or proximal necks can exaggerate steering problems.
Second, there is the concern that the balloon will burst from the application of pressurized cryofluid within, or the seal between the balloon and the body or shaft of the catheter will come undone (delamination). For the typically shaped catheter balloon, a balloon with a conical or ellipsoidal body and two necks, the outward pressure exerted on the balloon pushes the balloon material away from the catheter body or shaft. Longer necks with more attachment surface area are needed to securely attach the balloon to the catheter and prevent delamination due to the forces of pressure. This, in turn, creates longer balloons at the catheter distal tip that are more difficult to steer and precisely contact with target tissue.
In light of the above, it is the object of the present invention to provide a cryoablation catheter with a shortened distal tip that not only is more easily manipulated within small spaces, but that also includes a balloon that is more resistant to delamination from the catheter body or shaft by making use of the balloon pressure to help reduce the tensile stress on the sealing or bonding agent. Currently used devices with balloons having everted necks experience the opposite effect, with the balloon pressure contributing to delamination. Additionally, glue joints are not particularly good at resisting tensile stress, unless in compression. It is another object to provide a method of using a cryoablation catheter with a shortened distal tip.